长江河口北支建闸对减轻盐水入侵的数值模拟

doi:10.3969/j.issn.1000-5641.201941017

摘要/Abstract

摘要： 枯季长江河口盐水入侵的最大特色是北支盐水倒灌，它是南支东风西沙、太仓和陈行水库盐水的唯一来源，也是青草沙水库盐水的主要来源. 考虑潮汐和气候态1月和2月的径流量与风况，采用已严格验证过的长江河口盐水入侵三维数值模式，模拟和分析北支上段建闸前后盐水入侵的变化. 模拟结果表明：在北支上段建闸后，整个南支全为淡水，北支盐水倒灌南支的现象消失，北支上段盐度明显下降；在东风西沙、太仓和陈行水库取水口盐度接近0；在青草沙水库取水口盐度大幅下降，几乎所有时间盐度都低于0.45，全为淡水. 数值试验中，闸门的运行方式采用两种方案：全天落潮流期间开闸、夜里涨潮流期间关闸、白天涨潮流期间开闸，以及全天落潮流期间开闸、夜里和白天涨潮流期间关闸. 两者的试验结果中南支盐度变化几乎一致，原因在于前者的运行方式已经使得北支上段盐水入侵大幅减弱，出现盐度接近0.45的淡水区域；即使白天涨潮流期间开闸，其间进入南支的也是淡水，并且增加了南支向海的总余流. 从数值模拟的结果和闸门运行的成本考虑，推荐前者的北支建闸运行方案. 北支建闸极大地提高了上海东风西沙、陈行和青草沙水库取水时间，同样极大地提高了江苏太仓水库的取水时间，保障了两地的供水安全.

关键词: 长江河口, 盐水入侵, 水源地, 建闸, 数值模拟

Abstract: The most prominent feature of saltwater intrusion in the Changjiang Estuary is the saltwater spillover from the North Branch into the South Branch during the dry season; the spillover is the only source of saltwater for the Dongfengxisha, Taicang, and Chenhang Reservoirs as well as the main source of saltwater for the Qingcaosha Reservoir. A three dimensional numerical saltwater intrusion model, validated on the Changjiang Estuary, was applied to simulate and analyze salinity variation both during and after construction of the sluice at the upper reaches of the North Branch; the model considered tide, climatic river discharge, and wind in January and February. The simulated results showed that the South Branch is occupied by freshwater, the phenomenon of saltwater spillover from the North Branch vanishes and the salinity in the upper reaches of the North Branch decreases substantially after building the sluice. The salinity at the water intakes of the Dongfengxisha, Taicang, and Chenhang Reservoirs approaches 0. The salinity at the water intake of the Qingcaosha Reservoir decreases significantly and is less than 0.45 and there is freshwater at all time. The operation of the sluice in the numerical experiments is adopted in two ways. One is open during ebb current, closed during flood current in the daytime, and open during flood current in the nighttime. The other is open during ebb current and closed during flood current in the daytime and nighttime. The salinity variations in the South Branch with the two operational schemes are nearly identical. This can be attributed to the fact that the saltwater intrusion in the upper reaches of the North Branch is substantially reduced by the former sluice operational scheme, and a freshwater area with salinity approaching 0.45 appears. Even though the sluice is open during day flood current, the water entering the South Branch is freshwater and the total seaward residual current in the South Branch is enhanced. Considering the numerical simulation results and operation costs, the former sluice operational scheme is recommended. The water intake time is significantly improved, not only for the Dongfengxisha, Chenhang, and Qingcaosha Reservoirs in Shanghai, but also for the Taicang Reservoir in Jiangsu; moreover, security in water supply is ensured for both places.

Key words: Changjiang Estuary, saltwater intrusion, water sources, building sluice, numerical simulation

中图分类号:

P751

朱建荣, 鲁佩仪, 唐川敏, 陈晴, 吕行行. 长江河口北支建闸对减轻盐水入侵的数值模拟[J]. 华东师范大学学报（自然科学版）, 2020, 2020(3): 13-22.

ZHU Jianrong, LU Peiyi, TANG Chuanmin, CHEN Qing, Lü Hanghang. Numerical simulation of saltwater intrusion mitigation by building a sluice in the North Branch of the Changjiang Estuary[J]. Journal of East China Normal University(Natural Science), 2020, 2020(3): 13-22.

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